Generator and the generation of multiple frequencies



Feb. 27, 1923. 1,446,752 B. w. KENDALL GENERATOR AND THE GENERATION 0E MULTIPLE FREQUENCIES Filed Dec 29, 1916 2 sheets-sheet l I lnwnfor; 1 Burton W. Kpnda/l.

y 'Arr'y Feb. 27, 1923. 1,446,752 8. w. KENDALL I GENERATOR AND THE GENERATION OF MULTIPLE FREQUENCIES Filed Dec. 29, 1916 2 sheets-sheet 2 E B urfan W KeMda/A y AITy.

Patented Feb. 27, 1923.

UNITED STATES PATENT OFFICE.

BURTON W. KENDALL, OF NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

GENERATOR AND THE GENERATION OF MULTIPLE FREQUENCIES.

Application filed December 29, 1916. Serial No. 139,530.

To all whom it may concern:

Beit known that I, BURTON TV. Ki-zxnluln, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Generators and the Generation of Multiple Frequencies. of which the following is a full, clear, concise, and exact description.-

This invention relates to a method and meansfor the generation of multiple frequencies, and has for an object to'providea means for producing currents of a frequency or frequencies higher than a given basic frequency. The higher fretyuency currents may be used for any suitab e purpose, such as sources of carrier waves, for multiplex signaling. p

The higher frequency, currents are obtained by distorting the wave form of the fundamental frequency and by selecting the overtones or .rnultiple frequencies present in the distorted wave.

The distortion may beefi'ectedby means of an electricidischarge device which has the following characteristics t hat;give rise ,to a distortion. First, equal increments inthe voltage applied to the devicedo not produce proportionalchanges in itsoutput current. This gives rise to a distortiom'as the input voltage is not faithfully reproduced in the output circuit. This characteristic belongs to allaudions which have not been provided with speoial means to change this character istic.' Secondly, a further and greater dis-' tortion is obtained according to the present invention by considerably overloading the audion. This is done by applying to its input terminals an alternatingpotential such that the maximnm.,value carries the operation of the tube beyond thalt portionof its characteristic 4 which is substantially linear,

thus substantially distorting the wave form of the applied alternating potential as repeated bythe tube. This applied alternating potential may be such that-the maximum positive value will exceed that necessary to 'cause'th e tube to become saturated and the maximum negative value will exceed that negatiy' e .valu e' .requii 'ed to reduce the output current substantially to zero, or one of these conditions may cxistalone to the substantial exclusion of the other. The number of clue trons which can be givenoff by a thermionic cathode at a certain temperature has a limiting or saturation value. and the corresponding point on the characteristic curve of the electron discharge device may be termed the saturation point of the cathode for that tem perature. Accordingly the cathode will limit the space current whic can flow in the thermionic device and variations in the internal impedance in the circuit of the space current are not followed by proportionate changes in the value of space current. Thus the wave form of the output current will be considerably distorted. Thirdly, in somecases a further distortion may be obtained in'the'supprcssionjof the alternate half waves by pass ing the distorted wave through a unilaterally conductingdevice, such as a thermionic recti tier. A particular electric dischargedevicc may have one, two or even three of the distorting characteristics just described The harmonics selected may be'amplified to anyhigh power, value, and purified by means of tunedcircuits or filters which suppress the undesirable fr'e rquencies' iiind"se} lectively transmit theamplified overt'one of harmonic; M it v Various systems for carrying. out the invention are shown in the drawings,in which 'Fig, 1 shows diagrammatically an'oscillator of. the audion type which is considerably overloaded Ito produce a'j c'listo'rted wave form; 1'

Fig. 2 shows a-systemin' which a separate source of oscillations, is adapted-to s'uppl a thermionic device which may be consideralzily overloaded; f

Fig. 3 illustrates how 'the" generating scheme of Fig. 2fmay be combined with a selecting means shown in Fig}, Figs. fl and5 are modifi ations in which thermionic rectifiers are used. "I In Fig. l, 6 is any oscillation generator of the audiontype The generator may be of the form disclosed in the United States Patent No. 1,356,763to Ralph V. L. Hartley,

mental frequency of the oscillations supplied by the gencraixir 6 is determined by the adjustment of the variable condenser 21 in shunt to coils 7 and 8. Inductively related to the coils 7 and 8 is the coil 10, in circuit with which are the loop-resonantcircuits A, A, etc, each of which is tuned to a different multiple of the fundamental frequeneysupplied by the generator (i. The loop-resonant circuit A is tuned to the fimt overtone, which is the second multiple frequency, and this loop-resonant circuit comprising the condenser 11 and the inductance 12, accordingly provides a path of high im edance for currents at the fiist overtone an provides a. path of low impedance to currents of different frequencies. Similarly, each of the loop-resonant circuits A, A, etc, provides a, pathof low impedance to currents of frequencies difi'erent' from its resonant frequency, while the'r'esonant fro uenciesfl a're 'sup'plied i the out-going lines asoeiated with' 'tlieloop-resonant circuits. "By'jxhaps ofthe loop-resonant circuit A, thefilstoyettone is impressed on input circuit of one 'or morejamplifiers 13. adjustment of a vacuum tube of the a'ud1on' type for'its operation as a voltage or current amplifier isdes'cribed and claimed lathe 'patent to'Arnold, No. 1,329,283, January 27, 1920, for Thermionic amplifier. The output circuit of the amplifier 13 is con led bymeans offlthe transformer 14- toitllie 'filte'r 15 which selectively transmits the'aniplified first overtone to the line 16. The filter .15 is described and claimed in the United States Patent to Campbell, No. 1,227,113, patented May 22, 1917, for Improvements in electric wave filters. The second overtone, if desired, need not be amplified, and, accordingly, the line 17 may be directly connected to the loop-resonant circuit A. The amplifier 18, associated with the loop-resonant circuit A. is similar to the amplifier 13 above described. The armplified third overtone in the output circuit of the amplifier 18 may be purified or selectively transmitted by means of the eircuit 19' tuned to the frequency of this harmonic. The lines 1G, 17, 19, etc selectively transmit the segregated harmonics to suitable translating means not shown.

In 2 the generator 20 may be a higher frequency alternator or maybe an oscillator ofthe type described in connection with Fig. 1. The fgenerator 20 is coupled by means of trans ormer 21 to the input circuit of the thermionic repeater 22, the input circuit of which is tuned to the frequency supplied by the generator 20 by means of the condenser 23. Space current in the out put circuit of the repeater 22 is supplied by the battery 24. The output circuit of the repeater 22 is coupled by means ofthe transformer 25 to the line 26, bridged across which are the tuning condensers and induclanccs F. F and 1' tuned to the first. secoud and third m erti'n'ics. respectively. of the frequency supplied by the generator 2d. The tuning device F provides a path for currents of the fundamental frequency. means of the coil 39, inductivelyrelated to the coil 27 forming a part, of the tuning means F currents of the first orertone are transferred to the input circuit of the amplifier 28 similar to the amplifiers above dc scribed. The input circuit of amplifier 28 may be tuned to the first over-tone by means of the variable condenser 29. The output circuit of the amplifier 28 is coupled by means of the transformer 30 to the filter 31, which selectively transmits the amplified. first overtone to the line By means of circuit. 37. tuned to the second ovcrtonc. currents of this frequency may be. directly transmitted to the line 38 without ampli fication or further purification if desired. The circuit associated with the tuning means F, is similar to that associated with the tuning means F except that instead of using a filter such as 31. the tuned circuit may be used.

In Fig. 3 generator 20 and the thermionic repeater 22 are connected in amanner similar to that shown in Fig. 2 while the means for selecting the different harmonics from the output circuit of the repeater 22 are similar to those shown in Fig. 1.

In Fig. 4, instead of using a three-element audion tube to effect the distortion. the thermionic rectifier 36 may be used. Coupled with the rectifier 36 is the circuit arrangement for amplifying and selecting. as shoun in Figs. 1 and 3.

The modification disclosed in Fig. 5 is similar to that. shown in Fig. 4, except that the scheme of amplifying and purifying. as shown in Fig. 2, is used.

In each of the audions shown. an electron stream is established between the heated filament and the output electrode by means of the direct current source in the audion output circuit.

As to the operation of the systems disclosed in Figs. 1, 2 and 3, an alternating: voltage is supplied to the grid circuits of the thermionic devices 6 and 22 of such a high maximum value that for all voltage values above a given value, the output current is unresponsive thereto. This high in- 1 put voltage tends to produce greater variations in the output current than are possible under the limitations (1) that current can flow in but one direction in this circuit, and (2) that the magnitude of this current is limited to the number of available carriers, which depends on the operating conditions of the filament. A distortion of the wave form in the output circuitof the thermionic dcvice results and the various harmonics present may be selected, amplified and puri fied bv the means shown.

In igs. 4 and. 5, the distortion is effected by suppressing alternate half-Waves, as the rectifiers 36 are essentially unilaterally conducting, and further distortion may be secured by overloading. In this case also the harmonics present may be segregated, ainplified and purified.

In the figures, three different circuit arrangements have been shown for picking off certain harmonics, but it is obvious that any one of these arrangements may be used to select any one of the harmonics.

hat is claimed is:

1. The method of obtaining frequency harmonics of a base frequency comprising overloading a thermionic device.

2. The method of obtaining frequency harmonics of a base frequency comprising overloading an electric discharge device.

3. The method of obtaining frequency.

harmonics of a base frequency comprising overloading a vacuum electric device.

4. The method of harmonic generation which consists in overloading a thermionic device and selecting a harmonic compimcnt from the resulting distorted wave form.

The method of harmonic generation which consists in generating a non-snub soidal Wave form distorting said Wave form. selecting a harmonic component thereof. and purifying said component.

6. The method. of harmonic generation which consists in generating a non-sinusoidal Wave form, distorting said Wave form. selecting a harmonic component thereof. and selectively transmitting said component.

7. An arrangement for obtaining frequency harmonics of a base-frequency \vave comprising an electric discharge device having coupled input and output circuits and means for continuously overloading said de vice whereby an electroniotive force of the base frequency applied to said. input circuit is repeated to said output circuit as a dis torted \vavc comprising the desired has mouics.

8. An arrangement for obtaining l re quency harmonics of a base-frequency wave comprising a three-element electric discharge device having coupled input and output circuits and means for continuously overloading said device whereby a wave of the base frequency impressed upon said input circuit is repeated to said output circuit as a distorted \vave comprising the desired harmonics.

9. The method of alternating current production which comprises establishing an electron stream from a source of electrons operating in the region of its saturation point and periodically varying the iinpwL ancc prcsrntcd to said electron stream.

ill. series circuit including :i source of current, means for limiting the value of the current flowing in said circuit and a variable impedance, and means for )eriodica-lly vary ing the value of said impe ance.

11. A generator of distorted \vave forms comprising a thermionic device having an electron emitting cathode arranged to operatein the region of its saturation point, an input circuit connected to said cathode, and an output circuit coupled to said input circuit.

12. In combination, a generator of nonsinu soidal Waves of a base frequency and a circuit comprising a wave form distorting device connected thereto, said circuit also comprising means for selecting harmon cs, of the base frequency.

13. An electric system comprising a thermionic device of the vacuum tube type hav ing an input circuit and an output circuit coupled to said input circuit, a source of current for said output circuit, and means for overloading said device by supplying to said input circuit alternating potential of such high value that the current in the said output circuit is substantially unresponsive to an increase in said potential beyond a given value.

14. A harmonic generating system comprising a thermionic device of the vacuum tube type having an input circuit and an output circuit, a source of current for said output circuit, a source of alternating potential for said input circuit, and means associated with said output circuit for isolating a periodic component of the output current having a frequency harmonic to that of the potential supplied to said input circuit.

15. A harmonic generating system comprising a thermionic device of the vacuum tube type having an input circuit and an output circuit, a source of current for said output circuit, means for supplying an alternating potential to said input circuit and means associated with said output circuit for isolating a periodic component of the output current having a frequency harmonic to that of the potential supplied to said input circuit.

U). A harmonic generating system comprising a thermionic device of the vacuum tube type having an input circuit and an output circuit, a source of current for said output circuit, a source of alternating potential for said input circuit, means associated with said output circuit for selectively transmitting a periodic component of the output current having a frequency harmonic to that of the alternating potential supplied to said input circuit and means for amplifying said component.

17. A harmonic generating system comprising a thermionic device of the vacuum Yul-e type having an input circu t and an output circuit, a source of current for said output circuit, means for supplying an alternating potential to said input circuit, means associated with said output circuit tor selectively transmitting a periodic component of the output current having a frequency har monic to that of the potential supplied to said input circuit and means for amplifying sa d component.

19. In a harmonic generating system, the combination of a thermionic device of the :iudion type having an input circuit and an output circuit, a source of fundamental freq ency alternating potential for said input crcuit, means for tuning said input circuit to the frequency of said source, a Source of current for said output circuit, means for selecting a harmonic frequency from said output circuit, a thermionic amplifier having an input circuit and an output circuit. means for supplying said amplifier input circuit from said selecting means, and means for purifying the amplified harmonic frequency supplied by said amplifier.

In witness whereof, I hereunto suhscrioc my name this 28th day of December, A. l).

BURTON W. KEWDALL. 

